The present invention relates to a method for producing adhesive closing parts made of plastic and having adhesive closing elements which cooperate with corresponding adhesive closing elements of another adhesive closing part for the formation of an adhesive closing. The adhesive closing part with the adhesive closing elements is provided with at least a partial coating. The layer thickness of the partial coating is determined so that the subsequent formation of the adhesive closing is guaranteed.
A method for producing adhesive closing parts of plastic material is described in DE 196 46 318 A1. With that known production method, the adhesive closing part has a plurality of adhesive closing elements, each configured of one integral piece in the form of a stalk having a thickening or enlarged area. A thermoplastic, especially polyolefin or polyamide, is fed in plastic or liquid state into a gap between a platen and a grooved roll. The grooved roll is provided with outwardly and inwardly open hollow spaces. The two rolls are driven in rotation counter to one another. The grooved roll includes a screen with the hollow spaces produced by etching or by means of a laser. The adhesive closing elements do not come into being until the thermoplastic hardens in the open hollow spaces of the screen of the grooved roll. The thickenings or enlarged areas at the tops of the closing element stalks are configured in the form of mushroom heads having flattened out or concave depressions.
The adhesive closings produced in that manner are used most often in power vehicle technology, in soil working technology, for coverings of any sort and in some fields of special use in mechanical engineering. The adhesive closings have been proven in these areas as a detachable and operationally secure connection and closing technique.
EP-A-0418 951 introduces a method for producing adhesive closing elements for an adhesive closing in which the adhesive closing elements are provided with a coating of a pressure-sensitive adhesive. The adhesive coating is to heighten the adhesive and closing forces of the known adhesive closing.
Another method of this type is disclosed in EP-A-0829 563, in which the adhesive closing elements in the form of loops are provided with a coating with fluorocarbon. Such coating represents the base according to an impregnation method, in which the fluorocarbon penetrates into the plastic material of the adhesive closing elements. In that manner, the coating serves to repel the foam during foaming of the adhesive closing. The possibilities of use of such impregnated adhesive closing parts are limited.
Objects of the present invention are to provide an improved method for the production of adhesive closing parts of plastic material and having adhesive closing elements permitting adhesive closings with expanded ranges of possible uses.
According to the present invention, the coating for the adhesive closing elements is formed by a sol-gel method. A coating material is obtained which considerably broadens the possible uses for such adhesive closings. Thus, by means of the coating obtained by the sol-gel method, new and advantageous properties can be attributed to the closing.
The coating being applied by the sol-gel method is foam-resistant and works effectively counter to the possible penetration of the foam material during foaming, although the foam might have viscosities which are lower than that of water.
Furthermore, the coating applied by the sol-gel method can be constructed nano-compositionally. In other words, the layer thickness is extraordinarily minute. Thus, the coating medium can be of only a few molecules thickness. Because of this small layer thickness, the adhesive closing elements can indeed be completely covered, but are still not in any manner negatively influenced in their functionality. In other words, they can be connected with other adhesive closing elements, coated if desired, of another adhesive closing part for the formation of the adhesive closing.
Furthermore, the coating obtained by the sol-gel method can be provided with ferromagnetic properties. The very flat adhesive closing elements are preferably provided with plate-shaped ends that can be inserted manually without further difficulty into the foaming mold provided with magnets. The closing elements are then held securely by means of the magnetic forces of the coating medium, with the result that additional fixing devices can be abandoned or omitted.
Such additives, including those in the form of ferrites or magnetite materials, can be present in micro-encapsulated form, in other words as encapsulations of finely dispersed, liquid or solid phases formed by sheathing with film-forming polymers. The additives are deposited following emulsification and coacervation, or boundary layer or interfacial polymerization on the material to be sheathed.
Other objects, advantages and salient features of the present invention will become apparent from the following detailed description, which, taken in conjunction with the annexed drawings, discloses a preferred embodiment of the present invention.